2010 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 1 3 6 9 11 14 4 8 16 5 9 3 89 Monthly Average: 7.4 Partial 3 3 6 4 10 5 0 5 8 5 10 4 63 Monthly Average: 5.3 Spectroscopic 4 3 6 4 3 2 1 5 2 6 5 0 41 Monthly Average: 3.4 Cloudy 23 19 13 13 7 9 26 13 4 15 6 24 172 Monthly Average: 14.3 ------------------------------------------------------------------------------- Clear Hours 37 54 94 100 129 119 28 89 187 83 160 70 1150 Monthly Average: 95.8 Clear+Dark Hours 25 48 58 48 70 66 12 46 71 54 89 50 637 Monthly Average: 53.1 Mean Consec 1.0 1.5 1.2 2.3 2.2 2.8 4.0 2.0 3.2 1.7 1.3 1.0 Monthly Average: 2.0 Max Consec 1 2 2 4 4 5 4 3 6 3 2 1 Monthly Average: 3.1 ------------------------------------------------------------------------------- Definitions: Photometric - cloudfree dusk-to-dawn. Partial - at least 3 consecutive cloudfree hours during the night. Spectroscopic - less than about 1 mag. extinction throughout the night. Cloudy - cloudy. Clear+Dark Hours = photometric hours with moon absent. Mean Consec = mean number of consecutive photometric nights during the month. Max Consec = maximum number of consecutive photometric nights during the month.